As a child, George Dennehy questioned why God had him born armless and left in a Romanian orphanage as a newborn by parents who feared their small village wouldn't accept him.Dennehy, 18, of Ashland, Va., said Tuesday he believes his answer has come. He not only opened for alt-rockers the Goo Goo Dolls on the main stage at Musikfest, but also sang and accompanied the band on its song "Iris" by playing his guitar with his feet.About two weeks ago, a friend persuaded Dennehy to post a video of himself playing the song on the online social news site Reddit. Within 10 days, it had gone viral, gett